Autotroph

Under autotrophy (literally " self- eating ", from Ancient Greek αὐτός autos "self" and τροφή trophe " diet " ) is understood in biology, the ability of living organisms to build their building materials ( organic and reserve materials ) solely from inorganic substances. This fabric structure requires energy.

As autotrophic beings are primarily photosynthetic primary producers (especially plants) to call. With them light serves as an energy source ( photoautotrophy ). Some organisms may also chemical substance reactions as an energy source use ( Chemoautotrophie ).

The contrast to autotrophy is the heterotrophy, be used in the organic compounds for the construction of the building materials. Animals, fungi and many bacteria and archaea are heterotrophic. They feed either as consumers ( herbivores, carnivores or omnivores ) or they are decomposers.

Forms of autotrophy

The term Autotrophie usually refers to the carbon source of an organism. But organisms may be autotrophic also in relation to other building materials, for example, are nitrogen fixing bacteria in terms of their autotrophic nitrogen source.

According to the energy source, a distinction photoautotrophy and Chemoautotrophie.

Photoautotrophy

Photoautotrophy is the use of light as an energy source for autotrophy. Creatures with this ability are called photoautotroph. Almost all plants and algae and some bacteria, such as purple sulfur bacteria and green sulfur bacteria, walk with the help of chlorophyll - containing systems light energy into chemical energy (ATP) to ( prototrophy ) they for building construction and reserve materials from inorganic use substances ( see photosynthesis).

Chemoautotrophie

Chemoautotrophie is the use of chemical energy in autotrophy. Creatures with this ability are called chemoautotroph. Chemoautotrophie particularly occurs in bacteria and archaea. Examples are sulfur bacteria, nitrifying bacteria, some methanogens and other hydrogenotrophic bacteria. They use the energy that is released during the chemical reaction of inorganic substances to build up their construction and reserve substances from inorganic substances.

Chemoautotrophie is a special form of Chemotrophie, that is, the use of chemical energy, are at the only inorganic substances for energy converted (so-called chemical nutrition). Other names for this ability are also Lithotrophie or chemolithotrophy. The organisms with this ability are accordingly called lithotroph, chemolithotroph, or emphasizing the autotrophy as chemoautotroph or chemolithoautotrophically.

Biochemistry

Use carbon- autotrophic organisms for the formation of organic materials usually carbon dioxide CO2 as an inorganic carbon source. In some aquatic plants also the inclusion of carbonate ions could be detected. The inorganic carbon compounds, are reduced, and the carbon incorporated into organic compounds. The most important biological metabolic processes by means of which carbon dioxide is assimilated, are

• The Calvin cycle
• The reverse citric acid cycle and
• The carboxylation of pyruvate.

All plants assimilate carbon dioxide via the Calvin cycle, which is the most energy-consuming at the same time. Some microorganisms have different ways of carbon dioxide assimilation (for example, the reverse citric acid cycle ).

Also heterotrophic organisms can cover smaller proportions of their carbon requirements by carbon dioxide assimilation. This reaction is, for example, in the carboxylation of pyruvate at the beginning of gluconeogenesis or anaplerotic reaction for recovery of the citric acid cycle. For this reason, only those organisms are by definition as autotrophic, which cover their carbon requirements exclusively from inorganic sources.